1. Field of the Invention
This invention relates to a process for preparing fully drawn bicomponent fibers at high speeds and, more particularly, to a process of extruding two polyesters from a spinneret, passing the fibers through a cooling gas, drawing, heat-treating, and winding up the fibers at high speeds.
2. Description of Background Art
Synthetic bicomponent fibers are known. U.S. Pat. No. 3,671,379 discloses such fibers based on poly(ethylene terephthalate) and poly(trimethylene terephthalate). The spinning speeds disclosed in this reference are uneconomically slow. Japanese Patent Application Publication JP11-189923 and Japanese Patent JP61-32404 also disclose the use of copolyesters in making bicomponent fibers. U.S. Pat. No. 4,217,321 discloses spinning a bicomponent fiber based on poly(ethylene terephthalate) and poly(tetramethylene terephthalate) and drawing it at room temperature and low draw ratios. Such fibers, however, have low crimp levels, as do the polyester bicomponent fibers disclosed in U.S. Pat. No. 3,454,460.
Several apparatuses and methods have been proposed for melt-spinning partially oriented monocomponent fibers at high speeds, as disclosed in U.S. Pat. Nos. 4,687,610, 4,691,003, 5,034,182, and 5,824,248 and in International Patent Application WO95/15409. Generally, in these methods a cooling gas is introduced into a zone below the spinneret and accelerated in the travel direction of the newly formed fibers. However, such fibers do not crimp spontaneously and, therefore, do not have desirable high stretch-and-recovery properties.
An economical process for making highly crimpable polyester bicomponent fibers is still needed.